Wilding pines will cover a fifth of New Zealand within 20 years if they are not brought under control, Crown Research Institute Scion says.
Last year the government spent nearly $7 million poisoning the pest trees, which are infesting areas including high country Otago, Marlborough and the North Island central plateau.
Scion scientist Thomas Paul said the trees were still spreading at a rate of 90,000ha per year, and the situation was at the critical point.
Dr Paul said more funding from the government was needed before the problem got out of control.